A conventional probe apparatus includes a loader chamber and a prober chamber which are arranged adjacent to each other. The loader chamber has a cassette receiving part for receiving a cassette containing a plurality of objects to be inspected (e.g., semiconductor wafers W) therein, a wafer transfer mechanism for loading and unloading the wafers W into and from the cassette one by one and a pre-alignment mechanism for pre-aligning a semiconductor wafer. The prober chamber has a mounting table which is movable in X, Y, Z and θ directions while mounting thereon a semiconductor wafer, a probe card, which has probes, provided above the mounting table and an alignment mechanism for aligning the electrode pads of a semiconductor wafer with the probes.
The electrical characteristics of devices formed on a semiconductor wafer are inspected by bringing the probes into electrical contact with the electrode pads of a semiconductor wafer under the control of a control unit.
In performing the inspection, if necessary, one semiconductor wafer being inspected may be unloaded for sampling from a probe apparatus. In that case, the inspected semiconductor wafer is first transferred from the mounting table to, e.g., a wafer table provided below the cassette receiving part of the loader chamber, and then is unloaded from the wafer table. An example of the wafer table is disclosed in, e.g., Japanese Patent Laid-open Application No. H7-273159.
Further, when an inspection for electrical characteristics of the semiconductor wafer is performed, oxide films formed on surfaces of the electrode pads are scraped off to bring the probes of the probe card into electrical contact with the electrode pads of the semiconductor wafer and foreign materials, e.g., metal oxides thus generated during the contact are adhered to needle tips of the probes.
Conventionally, a polishing wafer W′ is mounted on a mounting table 1 as shown in FIG. 6A, and then is brought into slide-contact with probes 2A of a probe card 2 by lifting the mounting table 1 slightly as illustrated in, e.g., FIG. 6B. Accordingly, the needle tips of the probes 2A are polished, and particles, e.g., metal oxides and the like can be removed from the probes 2A.
Meanwhile, due to a recent trend that a diameter of a semiconductor wafer becomes increased and a size of the probe card 2 becomes enlarged, the foreign materials of the probes 2A may have to be removed in the middle of the inspection. In this case, for example, a buffer table provided under the cassette receiving part of the loader chamber has the polishing wafer W′ therein and, if necessary, the polishing wafer W′ is unloaded from the buffer table and mounted on the mounting table 1 by a wafer transfer mechanism, so that the probes 2A are polished by the polishing wafer W′ on the mounting table 1. After completing the polishing operation, the polishing wafer W′ is returned from the mounting table to the buffer table by the wafer transfer mechanism. The above polishing operation is automatically carried out.
The foreign materials removed by polishing the probes 2A can be adhered to a top surface of the polishing wafer W′. However, it is not possible to check a presence of foreign materials on a top surface of the polishing wafer W′ since the polishing operation of the probes 2A is automatically performed as described above. The foreign materials may also contain broken pieces from damaged parts of the probes 2A and the like. If a next polishing operation is performed with the foreign materials without being removed, the probes 2A may come into contact with the foreign materials and become bent, which leads to damages of the probe card. This may result in adverse influence on next inspection.